Conventional power module generally has a substrate as the bottom portion. Taking a power module having the power substrate as the bottom portion for example, the main structure of the power module includes the power substrate, a power chip, a connecting material, a bonding wire, a compound, a sealing material, a metal terminal and an outer housing structure. The power chip is disposed on the power substrate by the connecting material so as to accomplish the mechanical support of the power chip and dissipate the heat via the power substrate. The metal terminal is also connected to the power substrate by the connecting material and the electrodes of the power chip are connected to the power substrate by the bonding wire so as to accomplish the circuit conduction. Consequently, circuit of the power module is electrically connected with the external power and signal circuit by the metal terminal. In the entire structure of the power module, the outer housing structure further provides an accommodation space with the sealed bottom portion to be filled with the compound, so that the compound provides a protective environment and a protective insulation around the power chip.
In the conventional power module, the outer housing structure can be divided into two types. One is the integral forming structure and another is the multiple-parts housing structure. The integral forming housing structure includes a frame vertical to the power substrate and a cover parallel to the power substrate, wherein the frame and the cover are formed into the integral forming housing. The multiple-parts housing structure includes the frame and the cover formed separately. However, the above two types of the outer housing structures applied to the conventional power module have the fixed size and the accommodation space thereof is limited, so that accommodable power substrate is limited. If the fixed outer housing structure is used to accommodate a product with lower power level, the material of the power substrate and the compound will be wasted and the power density will be decreased. Consequently, the entire cost is increased and the power density of the system is influenced. On the other hand, in correspondence to new topology or power level, for the purposes of reducing the material cost and enhancing the power density of the system, the above two types of outer housing structures have to re-mold. Consequently, it will increase the extra cost for re-molding and the managing cost of the molding tools. The entire manufacturing cost can't be reduced.
Therefore, there is a need of providing a power module having a modular housing structure to overcome the above drawbacks.